In the Institute of Electrical and Electronics Engineers (IEEE) 802.11 ah standard, to extend a coverage area of an Access Point (AP), a relay device (Relay) is usually added between a Station (STA) and the AP, and an encrypted packet is forwarded between the STA and the AP by using the Relay. According to a standard implementation, a session key PTKrd is negotiated between the Relay and the STA, where Pairwise Transient Key (PTK) is a transient key between nodes, r represents the Relay, and d represents a downlink of the Relay. A session key PTKru is also negotiated between the Relay and the AP, where r represents the Relay, and u represents an uplink of the Relay. Generally, when the Relay forwards an encrypted uplink packet sent to the AP by the STA, the Relay first decrypts the encrypted uplink packet by using the PTKrd, and then encrypts the encrypted uplink packet by using the PTKru; when the Relay forwards an encrypted downlink packet sent to the STA by the AP, the Relay first decrypts the encrypted downlink packet by using the PTKru, and then encrypts the encrypted downlink packet by using the PTKrd.
The foregoing processing process in which the Relay needs to perform decryption and then perform encryption when forwarding an encrypted packet between the STA and the AP needs to occupy some processing time, which reduces channel utilization and increases additional power consumption of the Relay.